Solar Control Coating With High Solar Heat Gain Coefficient

ABSTRACT

A coating provides a high solar heat gain coefficient (SHGC) and a low overall heat transfer coefficient (U-value) to trap and retain solar heat. The coating and coated article are particularly useful for use in architectural transparencies in northern climates. The coating includes a first dielectric layer; a continuous metallic layer formed over at least a portion of the first dielectric layer, the metallic layer having a thickness less than 8 nm; a primer layer formed over at least a portion of the metallic layer; a second dielectric layer formed over at least a portion of the primer layer; and an overcoat formed over at least a portion of the second dielectric layer. When used on a No. 3 surface of a reference IGU, the coating provides a SHGC of greater than or equal to 0.6 and a U-value of less than or equal to 0.35.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/774,751, filed on May 6, 2010, which claims priority to U.S. PatentApplication Ser. No. 61/176,534, filed May 8, 2009, the disclosures ofwhich are herein incorporated by reference in their entireties.

BACKGROUND OF THE INVENTION Field of the Invention

This invention relates generally to solar control coatings and, in oneparticular embodiment, to a solar control coating providing a high solarheat gain coefficient (SHGC) and a low overall heat transfer coefficient(U-value).

Technical Considerations

The SHGC is the fraction of incident solar radiation admitted through awindow, both directly transmitted, and absorbed and subsequentlyreleased inwardly. The lower the SHGC, the less solar heat istransmitted. The U-value is a measure of the rate of non-solar heat lossor gain through a material. The lower the U-value, the greater theresistance to heat flow and the better the insulating value.

Solar control coatings are known in the fields of architectural andautomotive transparencies. These solar control coatings block or filterselected ranges of electromagnetic radiation, such as in the range ofsolar infrared or solar ultraviolet radiation, to reduce the amount ofsolar energy entering the vehicle or building. This reduction of solarenergy transmittance helps reduce the load on the cooling units of thevehicle or building, particularly in the summer months. Conventionalsolar control coatings typically provide a relatively low SHGC.

While low SHGC coatings are advantageous in southern climates, they maynot be as desirable in northern climates. For northern climates, it maybe more energy efficient to have windows with a higher SHGC to trap moreheat from the sun inside the building during the winter months. This isparticularly true in northern climates where the cooler days of fall andwinter weather outnumber the warmer days of spring and summer.

Therefore, it would be desirable to provide a coating and/or coatedarticle that improves the energy efficiency of a building in a northernclimate where the desire is to trap heat from the sun inside thebuilding. The coating and/or coated article can have a low emissivity togive a low U-value while having a high SHGC so as to let more solar heatinto the building and keep it there.

SUMMARY OF THE INVENTION

A coating provides a high solar heat gain coefficient (SHGC) and a lowoverall heat transfer coefficient (U-valve) to trap and retain solarheat. The coating and coated article are particularly useful forarchitectural transparencies in northern climates.

A coated transparency comprises a substrate and a coating formed over atleast a portion of the substrate. The coating comprises a firstdielectric layer formed over at least a portion of the substrate; acontinuous metallic layer formed over at least a portion of the firstdielectric layer, the metallic layer having a thickness less than 8 nm;a primer layer formed over at least a portion of the metallic layer; asecond dielectric layer formed over at least a portion of the primerlayer; and an overcoat formed over at least a portion of the seconddielectric layer. The coating, when used on the No. 3 surface of areference IGU, provides a SHGC of greater than or equal to 0.6 and aU-value of less than or equal to 0.35.

In one exemplary coating, the first dielectric layer has a thickness inthe range of 40 nm to 50 nm. The first dielectric layer comprises a zincoxide film deposited over a zinc stannate film, the zinc oxide film hasa thickness in the range of 3 nm to 15 nm, and the zinc stannate filmhas a thickness in the range of 25 nm to 40 nm. The metallic layercomprises silver having a thickness less than or equal to 7.5 nm. Theprimer layer comprises titanium. The second dielectric layer has athickness in the range of 30 nm to 40 nm. The second dielectric layercomprises a zinc oxide film and a zinc stannate film deposited over thezinc oxide film. The zinc oxide film has a thickness in the range of 3nm to 15 nm. The overcoat has a thickness in the range of 2 nm to 6 nmand comprises titania. The coating, when used on the No. 3 surface of areference IGU, provides a SHGC of greater than or equal to 0.6, such asgreater than or equal to 0.65 and a U-value of less than or equal to0.35, such as less than or equal to 0.33.

In another exemplary coating, the first dielectric layer comprises afirst layer comprising zinc stannate, a second layer comprising zincoxide, a third layer comprising zinc stannate, and a fourth layercomprising zinc oxide, wherein the first dielectric layer has athickness in the range of 44 nm to 48 nm, the first layer and thirdlayer each have a thickness in the range of 16 nm to 17 nm, and thesecond layer and fourth layer each have a thickness in the range of 6 nmto 8 nm. The metallic layer comprises silver having a thickness lessthan or equal to 7 nm. The primer layer comprises titanium. The seconddielectric layer comprises a first layer comprising zinc oxide, a secondlayer comprising zinc stannate, a third layer comprising zinc oxide, anda fourth layer comprising zinc stannate, wherein the second dielectriclayer has a thickness in the range of 30 nm to 35 nm, the first layerand third layer each have a thickness in the range of 3 nm to 5 nm, andthe second layer and fourth layer each have a thickness in the range of11 nm to 12 nm. The overcoat has a thickness in the range of 5 nm to 10nm and comprises titania. The coating, when used on the No. 3 surface ofa reference IGU, provides a SHGC of greater than or equal to 0.6, suchas greater than or equal to 0.65 and a U-value of less than or equal to0.35, such as less than or equal to 0.33.

An insulating glass unit comprises a first substrate having a No. 1surface and a No. 2 surface, and a second substrate spaced from thefirst substrate and having a No. 3 surface and a No. 4 surface, with theNo. 3 surface facing the No. 2 surface. A coating is formed over atleast a portion of the No. 3 surface. The coating comprises a firstdielectric layer formed over at least a portion of the substrate; acontinuous metallic layer formed over at least a portion of the firstdielectric layer, wherein the metallic layer comprises silver having athickness less than or equal to 7.5 nm; a primer layer formed over atleast a portion of the metallic layer, wherein the primer film comprisestitanium; a second dielectric layer formed over at least a portion ofthe primer layer; and an overcoat formed over at least a portion of thesecond dielectric layer. The insulating glass unit has a SHGC of greaterthan or equal to 0.6, such as greater than or equal to 0.65 and aU-value of less than or equal to 0.35, such as less than or equal to0.33. In one example, the first dielectric layer has a thickness in therange of 40 nm to 50 nm, the first dielectric layer comprises a zincoxide film deposited over a zinc stannate film, the zinc oxide film hasa thickness in the range of 3 nm to 15 nm, and the zinc stannate filmhas a thickness in the range of 25 nm to 40 nm. The metallic layercomprises silver having a thickness less than or equal to 7.5 nm. Theprimer film comprises titanium. The second dielectric layer comprises azinc oxide film and a zinc stannate film deposited over the zinc oxidefilm, the second dielectric layer has a thickness in the range of 30 nmto 40 nm, and the zinc oxide film has a thickness in the range of 3 nmto 15 nm. The overcoat has a thickness in the range of 2 nm to 6 nm andcomprises titania. In another insulating glass unit, the firstdielectric layer comprises a first layer comprising zinc stannate, asecond layer comprising zinc oxide, a third layer comprising zincstannate, and a fourth layer comprising zinc oxide, wherein the firstdielectric layer has a thickness in the range of 44 nm to 48 nm, thefirst layer and third layer each have a thickness in the range of 16 nmto 17 nm, and the second layer and fourth layer each have a thickness inthe range of 6 nm to 8 nm. The metallic layer comprises silver having athickness less than or equal to 7 nm. The primer film comprisestitanium. The second dielectric layer comprises a first layer comprisingzinc oxide, a second layer comprising zinc stannate, a third layercomprising zinc oxide, and a fourth layer comprising zinc stannate,wherein the second dielectric layer has a thickness in the range of 30nm to 35 nm, the first layer and third layer each have a thickness inthe range of 3 nm to 5 nm, and the second layer and fourth layer eachhave a thickness in the range of 11 nm to 12 nm. The overcoat has athickness in the range of 5 nm to 10 nm and comprises titania.

Another insulating glass unit comprises a first substrate having a No. 1surface and a No. 2 surface; a second substrate spaced from the firstsubstrate and having a No. 3 surface and a No. 4 surface, with the No. 3surface facing the No. 2 surface; and a third substrate spaced from thesecond substrate and having a No. 4 surface and a No. 5 surface. A firstcoating is formed over at least a portion of the No. 5 surface. Thefirst coating comprises a first dielectric layer formed over at least aportion of the substrate; a continuous metallic layer formed over atleast a portion of the first dielectric layer; a primer layer formedover at least a portion of the metallic layer; a second dielectric layerformed over at least a portion of the primer layer; and an overcoatformed over at least a portion of the second dielectric layer, whereinthe overcoat has a thickness in the range of 2 nm to 6 nm and theovercoat comprises titania. A second coating is formed over at least aportion of the No. 2 surface, the second coating comprising at least twometallic silver layers separated by dielectric layers. The insulatingglass unit has a SHGC of greater than or equal to 0.6, such as greaterthan or equal to 0.65 and a U-value of less than or equal to 0.35, suchas less than or equal to 0.33. In one example, the first dielectriclayer of the first coating has a thickness in the range of 40 nm to 50nm, the first dielectric layer comprises a zinc oxide film depositedover a zinc stannate film, the zinc oxide film has a thickness in therange of 3 nm to 15 nm, and the zinc stannate film has a thickness inthe range of 25 nm to 40 nm. The metallic layer of the first coatingcomprises silver having a thickness less than or equal to 7.5 nm. Theprimer film of the first coating comprises titanium. The seconddielectric layer of the first coating comprises a zinc oxide film and azinc stannate film deposited over the zinc oxide film, the seconddielectric layer has a thickness in the range of 30 nm to 40 nm, and thezinc oxide film has a thickness in the range of 3 nm to 15 nm. Theovercoat of the first coating has a thickness in the range of 2 nm to 6nm and comprises titania. In another example, the first dielectric layerof the first coating comprises a first layer comprising zinc stannate, asecond layer comprising zinc oxide, a third layer comprising zincstannate, and a fourth layer comprising zinc oxide, wherein the firstdielectric layer has a thickness in the range of 44 nm to 48 nm, thefirst layer and third layer each have a thickness in the range of 16 nmto 17 nm, and the second layer and fourth layer each have a thickness inthe range of 6 nm to 8 nm. The metallic layer of the first coatingcomprises silver having a thickness less than or equal to 7 nm. Theprimer film of the first coating comprises titanium. The seconddielectric layer of the first coating comprises a first layer comprisingzinc oxide, a second layer comprising zinc stannate, a third layercomprising zinc oxide, and a fourth layer comprising zinc stannate,wherein the second dielectric layer has a thickness in the range of 30nm to 35 nm, the first layer and third layer each have a thickness inthe range of 3 nm to 5 nm, and the second layer and fourth layer eachhave a thickness in the range of 11 nm to 12 nm. The overcoat of thefirst coating has a thickness in the range of 5 nm to 10 nm and theovercoat comprises titania.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the following drawingfigures wherein like reference numbers identify like parts throughout.

FIG. 1 is a side view (not to scale) of an insulating glass unit (IGU)having a coating of the invention;

FIG. 2 is a side view (not to scale) of a coating incorporating featuresof the invention;

FIG. 3 is a side view (not to scale) of another coating incorporatingfeatures of the invention; and

FIG. 4 is a side view (not to scale) of another insulating glass unit(IGU) having a coating of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As used herein, spatial or directional terms, such as “left”, “right”,“inner”, “outer”, “above”, “below”, and the like, relate to theinvention as it is shown in the drawing figures. However, it is to beunderstood that the invention can assume various alternativeorientations and, accordingly, such terms are not to be considered aslimiting. Further, as used herein, all numbers expressing dimensions,physical characteristics, processing parameters, quantities ofingredients, reaction conditions, and the like, used in thespecification and claims are to be understood as being modified in allinstances by the term “about”. Accordingly, unless indicated to thecontrary, the numerical values set forth in the following specificationand claims may vary depending upon the desired properties sought to beobtained by the present invention. At the very least, and not as anattempt to limit the application of the doctrine of equivalents to thescope of the claims, each numerical value should at least be construedin light of the number of reported significant digits and by applyingordinary rounding techniques. Moreover, all ranges disclosed herein areto be understood to encompass the beginning and ending range values andany and all subranges subsumed therein. For example, a stated range of“1 to 10” should be considered to include any and all subranges between(and inclusive of) the minimum value of 1 and the maximum value of 10;that is, all subranges beginning with a minimum value of 1 or more andending with a maximum value of 10 or less, e.g., 1 to 3.3, 4.7 to 7.5,5.5 to 10, and the like. Further, as used herein, the terms “formedover”, “deposited over”, or “provided over” mean formed, deposited, orprovided on but not necessarily in contact with the surface. Forexample, a coating layer “formed over” a substrate does not preclude thepresence of one or more other coating layers or films of the same ordifferent composition located between the formed coating layer and thesubstrate. The terms “visible region” or “visible light” refer toelectromagnetic radiation having a wavelength in the range of 380 nm to800 nm. The terms “infrared region” or “infrared radiation” refer toelectromagnetic radiation having a wavelength in the range of greaterthan 800 nm to 100,000 nm. The terms “ultraviolet region” or“ultraviolet radiation” mean electromagnetic energy having a wavelengthin the range of 300 nm to less than 380 nm. Additionally, all documents,such as, but not limited to, issued patents and patent applications,referred to herein are to be considered to be “incorporated byreference” in their entirety. As used herein, the term “film” refers toa coating region of a desired or selected coating composition. A “layer”can comprise one or more “films”, and a “coating” or “coating stack” cancomprise one or more “layers”. U-values herein are expressed forNFRC/ASHRAE winter conditions of 0° F. (−18° C.) outdoor temperature,70° F. (21° C.) indoor temperature, 15 miles per hour wind, and no solarload.

For purposes of the following discussion, the invention will bediscussed with reference to use with an architectural transparency, suchas, but not limited to, an insulating glass unit (IGU). As used herein,the term “architectural transparency” refers to any transparency locatedon a building, such as, but not limited to, windows and sky lights.However, it is to be understood that the invention is not limited to usewith such architectural transparencies but could be practiced withtransparencies in any desired field, such as, but not limited to,laminated or non-laminated residential and/or commercial windows, and/ortransparencies for land, air, space, above water and under watervehicles. Therefore, it is to be understood that the specificallydisclosed exemplary embodiments are presented simply to explain thegeneral concepts of the invention and that the invention is not limitedto these specific exemplary embodiments. Additionally, while a typical“transparency” can have sufficient visible light transmission such thatmaterials can be viewed through the transparency, in the practice of theinvention the “transparency” need not be transparent to visible lightbut may be translucent or opaque (as described below).

A non-limiting transparency 10 incorporating features of the inventionis illustrated in FIG. 1. The transparency 10 can have any desiredvisible light, infrared radiation, or ultraviolet radiation transmissionand/or reflection. For example, the transparency 10 can have a visiblelight transmission of any desired amount, e.g., greater than 0% up to100%.

The exemplary transparency 10 of FIG. 1 is in the form of a conventionaltwo-ply insulating glass unit and includes a first ply 12 with a firstmajor surface 14 (No. 1 surface) and an opposed second major surface 16(No. 2 surface). In the illustrated non-limiting embodiment, the firstmajor surface 14 faces the building exterior, i.e., is an outer majorsurface, and the second major surface 16 faces the interior of thebuilding. The transparency 10 also includes a second ply 18 having anouter (first) major surface 20 (No. 3 surface) and an inner (second)major surface 22 (No. 4 surface) and spaced from the first ply 12. Thisnumbering of the ply surfaces is in keeping with conventional practicein the fenestration art. The first and second plies 12, 18 can beconnected together in any suitable manner, such as by being adhesivelybonded to a conventional spacer frame 24. A gap or chamber 26 is formedbetween the two plies 12, 18. The chamber 26 can be filled with aselected atmosphere, such as air, or a non-reactive gas, such as argonor krypton gas. A solar control coating 30 of the invention is formedover at least a portion of one of the plies 12, 18, such as, but notlimited to, over at least a portion of the No. 2 surface 16 or at leasta portion of the No. 3 surface 20. Although, the coating could also beon the No. 1 surface or the No. 4 surface, if desired. Examples ofinsulating glass units are found, for example, in U.S. Pat. Nos.4,193,236; 4,464,874; 5,088,258; and 5,106,663.

In the broad practice of the invention, the plies 12, 18 of thetransparency 10 can be of the same or different materials. The plies 12,18 can include any desired material having any desired characteristics.For example, one or more of the plies 12, 18 can be transparent ortranslucent to visible light. By “transparent” is meant having visiblelight transmission of greater than 0% up to 100%. Alternatively, one ormore of the plies 12, 18 can be translucent. By “translucent” is meantallowing electromagnetic energy (e.g., visible light) to pass throughbut diffusing this energy such that objects on the side opposite theviewer are not clearly visible. Examples of suitable materials include,but are not limited to, plastic substrates (such as acrylic polymers,such as polyacrylates; polyalkylmethacrylates, such aspolymethylmethacrylates, polyethylmethacrylates,polypropylmethacrylates, and the like; polyurethanes; polycarbonates;polyalkylterephthalates, such as polyethyleneterephthalate (PET),polypropyleneterephthalates, polybutyleneterephthalates, and the like;polysiloxane-containing polymers; or copolymers of any monomers forpreparing these, or any mixtures thereof); ceramic substrates; glasssubstrates; or mixtures or combinations of any of the above. Forexample, one or more of the plies 12, 18 can include conventionalsoda-lime-silicate glass, borosilicate glass, or leaded glass. The glasscan be clear glass. By “clear glass” is meant non-tinted or non-coloredglass. Alternatively, the glass can be tinted or otherwise coloredglass. The glass can be annealed or heat-treated glass. As used herein,the term “heat treated” means tempered or at least partially tempered.The glass can be of any type, such as conventional float glass, and canbe of any composition having any optical properties, e.g., any value ofvisible transmission, ultraviolet transmission, infrared transmission,and/or total solar energy transmission. By “float glass” is meant glassformed by a conventional float process in which molten glass isdeposited onto a molten metal bath and controllably cooled to form afloat glass ribbon. Examples of float glass processes are disclosed inU.S. Pat. Nos. 4,466,562 and 4,671,155.

The first and second plies 12, 18 can each be, for example, clear floatglass or can be tinted or colored glass or one ply 12, 18 can be clearglass and the other ply 12, 18 colored glass. Although not limiting tothe invention, examples of glass suitable for the first ply 12 and/orsecond ply 18 are described in U.S. Pat. Nos. 4,746,347; 4,792,536;5,030,593; 5,030,594; 5,240,886; 5,385,872; and 5,393,593. The first andsecond plies 12, 18 can be of any desired dimensions, e.g., length,width, shape, or thickness. In one exemplary transparency, the first andsecond plies can each be 1 mm to 10 mm thick, such as 1 mm to 8 mmthick, such as 2 mm to 8 mm, such as 3 mm to 7 mm, such as 5 mm to 7 mm,such as 6 mm thick. Non-limiting examples of glass that can be used forthe practice of the invention include clear glass, Starphire®,Solargreen®, Solextra®, GL-20®, GL35™, Solarbronze®, Solargray® glass,Pacifica® glass, SolarBlue® glass, Solarphire® glass, Solarphire PV®glass, and Optiblue® glass, all commercially available from PPGIndustries Inc. of Pittsburgh, Pa.

The coating 30 of the invention is deposited over at least a portion ofat least one major surface of one of the glass plies 12, 18. In theexample shown in FIG. 1, the coating 30 is formed over at least aportion of the outer surface 20 of the inboard glass ply 18. The coating30 is configured to be a low emissivity coating that admits and retainssolar heat.

The coating 30 can be deposited by any conventional method, such as, butnot limited to, conventional chemical vapor deposition (CVD) and/orphysical vapor deposition (PVD) methods. Examples of PVD processesinclude thermal or electron beam evaporation and vacuum sputtering (suchas magnetron sputter vapor deposition (MSVD)). Other coating methodscould also be used, such as, but not limited to, sol-gel deposition. Inone non-limiting embodiment, the coating 30 can be deposited by MSVD.Examples of MSVD coating devices and methods will be well understood byone of ordinary skill in the art and are described, for example, in U.S.Pat. Nos. 4,379,040; 4,861,669; 4,898,789; 4,898,790; 4,900,633;4,920,006; 4,938,857; 5,328,768; and 5,492,750.

An exemplary non-limiting coating 30 of the invention is shown in FIG.2. This exemplary coating 30 includes a base layer or first dielectriclayer 40 deposited over at least a portion of a major surface of asubstrate (e.g., the No. 3 surface 20 of the second ply 18). The firstdielectric layer 40 can be a single layer or can comprise more than onefilm of antireflective materials and/or dielectric materials, such as,but not limited to, metal oxides, oxides of metal alloys, nitrides,oxynitrides, or mixtures thereof. The first dielectric layer 40 can betransparent to visible light. Examples of suitable metal oxides for thefirst dielectric layer 40 include oxides of titanium, hafnium,zirconium, niobium, zinc, bismuth, lead, indium, tin, and mixturesthereof. These metal oxides can have small amounts of other materials,such as manganese in bismuth oxide, tin in indium oxide, etc.Additionally, oxides of metal alloys or metal mixtures can be used, suchas oxides containing zinc and tin (e.g., zinc stannate), oxides ofindium-tin alloys, silicon nitrides, silicon aluminum nitrides, oraluminum nitrides. Further, doped metal oxides, such as antimony orindium doped tin oxides or nickel or boron doped silicon oxides, can beused. The first dielectric layer 40 can be a substantially single phasefilm, such as a metal alloy oxide film, e.g., zinc stannate, or can be amixture of phases composed of zinc and tin oxides or can be composed ofa plurality of films.

The first dielectric layer 40 (whether a single film or multiple filmlayer) can have a thickness in the range of 20 nanometers (nm) to 70 nm,such as 20 nm to 60 nm, such as 30 nm to 60 nm, such as 40 nm to 55 nm,such as 44 nm to 46 nm, such as 45 nm.

As shown in FIG. 2, the first dielectric layer 40 can comprise amulti-film structure having a first film 42, e.g., a metal alloy oxidefilm, deposited over at least a portion of a substrate (such as theouter major surface 20 of the second ply 18) and a second film 44, e.g.,a metal oxide or oxide mixture film, deposited over the first metalalloy oxide film 42. In one non-limiting embodiment, the first film 42can be a zinc/tin alloy oxide. By “zinc/tin alloy oxide” is meant bothtrue alloys and also mixtures of the oxides. The zinc/tin alloy oxidecan be that obtained from magnetron sputtering vacuum deposition from acathode of zinc and tin. One non-limiting cathode can comprise zinc andtin in proportions of 5 wt. % to 95 wt. % zinc and 95 wt. % to 5 wt. %tin, such as 10 wt. % to 90 wt. % zinc and 90 wt. % to 10 wt. % tin.However, other ratios of zinc to tin could also be used. One suitablemetal alloy oxide that can be present in the first film 42 is zincstannate. By “zinc stannate” is meant a composition ofZn_(x)Sn_(1-x)O_(2-x) (Formula 1) where “x” varies in the range ofgreater than 0 to less than 1. For instance, “x” can be greater than 0and can be any fraction or decimal between greater than 0 to lessthan 1. For example, where x=2/3, Formula 1 is Zn_(2/3)Sn_(1/3)O_(4/3),which is more commonly described as “Zn₂SnO₄”. A zincstannate-containing film has one or more of the forms of Formula 1 in apredominant amount in the film.

The second film 44 can be a metal oxide film, such as zinc oxidecontaining film. The zinc oxide film can be deposited from a zinccathode that includes other materials to improve the sputteringcharacteristics of the cathode. For example, the zinc cathode caninclude a small amount (e.g., up to 10 wt. %, such as up to 5 wt. %) oftin to improve sputtering. In which case, the resultant zinc oxide filmwould include a small percentage of tin oxide, e.g., up to 10 wt. % tinoxide, e.g., up to 5 wt. % tin oxide. A coating layer deposited from azinc cathode having up to 10 wt. % tin (added to enhance theconductivity of the cathode) is referred to herein as “a zinc oxidefilm” even though a small amount of tin may be present. The small amountof tin in the cathode (e.g., less than or equal to 10 wt. %, such asless than or equal to 5 wt. %) is believed to form tin oxide in thepredominantly zinc oxide second film 44.

The first film 42 can comprise zinc stannate having a thickness in therange of 20 nm to 60 nm, such as 25 nm to 50 nm, such as 35 nm to 40 nm.The second film 44 can comprise zinc oxide (for example, 90 wt. % zincoxide and 10 wt. % tin oxide) having a thickness in the range of 3 nm to15 nm, such as 5 nm to 10 nm.

A heat and/or radiation reflective metallic layer 46 can be depositedover the first dielectric layer 40. The reflective layer 46 can includea reflective metal, such as, but not limited to, gold, copper, platinum,osmium, titanium, nickel, chromium, palladium, aluminum, silver, ormixtures, alloys, or combinations thereof. In one embodiment, thereflective layer 46 comprises a metallic silver layer having a thicknessin the range of 3 nm to 8 nm, such as 4 nm to 8 nm, such as 5 nm to 7nm, such as 6 nm to 7 nm. The metallic layer 46 is a continuous layer.

A first primer layer 48 is located over the reflective layer 46. Thefirst primer layer 48 can be a single film or a multiple film layer. Thefirst primer layer 48 can include an oxygen-capturing material that canbe sacrificial during the deposition process to prevent degradation oroxidation of the first reflective layer 46 during the sputtering processor subsequent heating processes. Examples of materials useful for thefirst primer layer 48 include metals or oxides of metals, such astitanium, zirconium, copper, nickel, chromium, aluminum; silicon,silicon dioxide, silicon nitride, silicon oxynitride, nickel-chromealloys (such as Inconel), zirconium, aluminum, alloys of silicon andaluminum, alloys containing cobalt and chromium (e.g., Stellite), andmixtures thereof. For example, the first primer layer 48 can be titaniumhaving a thickness in the range of 0.5 to 3 nm, such as 0.5 to 2 nm,such as 1 nm to 2 nm, such as 1.4 nm.

For the primer layer 48, it should be appreciated that the layer isformed by first depositing a metal. At least a portion of the metal isoxidized during further processing of the coating 30. In the case of anannealed coating (Examples 1 and 3 below), the titanium primer layer isoxidized during subsequent deposition of overlying oxide layers. In thecase of a temperable coating (Examples 2 and 4 below), a portion of thetitanium is oxidized during subsequent deposition of oxide layers andthe remainder is oxidized upon tempering.

A second dielectric layer 50 is located over the reflective layer 46(e.g., over the first primer layer 48). The second dielectric layer 50comprises one or more metal oxide or metal alloy oxide-containing films,such as those described above with respect to the first dielectric layer40. For example, the second dielectric layer 50 can include a firstmetal oxide film 52, e.g., a zinc oxide film (for example, 90 wt. % zincoxide and 10 wt. % tin oxide), deposited over the first primer film 48and a second metal alloy oxide film 54, e.g., a zinc stannate film,deposited over the first zinc oxide film 52.

The second dielectric layer 50 can have a total thickness (e.g., thecombined thicknesses of the layers) in the range of 10 nm to 50 nm, suchas 20 nm to 50 nm, such as 30 nm to 50 nm, such as 30 nm to 40 nm, suchas 35 nm to 40 nm, such as 36.2 nm.

For example, the zinc oxide film 52 can have a thickness in the range of3 nm to 15 nm, such as 5 nm to 10 nm. The metal alloy oxide layer (zincstannate) 54 can have a thickness in the range of 15 nm to 35 nm, suchas 20 nm to 35 nm, such as 21 nm to 31 nm.

An overcoat 60 can be located over the second dielectric layer 50. Theovercoat 60 can help protect the underlying coating layers frommechanical and chemical attack. The overcoat 60 can be, for example, oneor more metal oxide or metal nitride layers. Examples of suitablematerials include oxides and/or nitrides of silicon, titanium, aluminum,zirconium, and mixtures thereof, for example a mixture of silica andalumina. For example, the overcoat 60 can be titania having a thicknessin the range of 1 nm to 10 nm, such as 2 nm to 8 nm, such as 4 nm to 6nm, such as 5 nm.

The coating 30 can also include an optional protective coating 70. Theprotective coating 70 assists in protecting the underlying layers frommechanical and chemical attack during manufacture, transit, handling,processing, and/or during the mirror's service life in the field. Theprotective coating 70 also helps protect the underlying layers from theingress of liquid water, water vapor, and other environmental pollutants(be they solid, liquid or gas).

The protective coating 70 can be an oxygen barrier coating layer toprevent or reduce the passage of ambient oxygen into the underlyinglayers during subsequent processing, e.g., such as during heating orbending. The protective coating 70 can be of any desired material ormixture of materials, such as, but not limited to, one or more inorganicmaterials. In one exemplary embodiment, the protective coating 70 caninclude a layer having one or more metal oxide materials, such as, butnot limited to, oxides of aluminum, silicon, or mixtures thereof. Forexample, the protective coating 70 can be a single coating layercomprising silica, alumina, or mixtures thereof. For example, theprotective coating 70 can include silica and alumina in the range of 70wt. % to 99 wt. % silica and 1 wt. % to 30 wt. % alumina, such as 75 wt.% to 90 wt. % silica and 25 wt. % to 10 wt. % alumina, such as 80 wt. %to 90 wt. % silica and 20 wt. % to 10 wt. % alumina, such as 85 wt. % to90 wt. % silica and 15 wt. % to 10 wt. % alumina, In one particularnon-limiting embodiment, the protective coating 70 comprises 85 wt. %silica and 15 wt. % alumina. Other materials, such as aluminum,chromium, hafnium, yttrium, nickel, boron, phosphorous, titanium,zirconium, and/or oxides thereof, can also be present, such as to adjustthe refractive index of the protective coating 70. The protectivecoating 70 can be of non-uniform thickness. By “non-uniform thickness”is meant that the thickness of the protective coating 70 can vary over agiven unit area, e.g., the protective coating 70 can have high and lowspots or areas. The protective coating 70 can have a thickness in therange of 1 nm to 1,000 nm, such as 10 nm to 500 nm, such as 20 nm to 300nm, such as 50 nm to 300 nm, e.g., 50 nm to 200 nm, such as 50 nm to 150nm, such as 50 nm to 120 nm, such as 75 nm to 120 nm such as 75 nm to100 nm. In a particular non-limiting embodiment, the protective coating50 can have a thickness of at least 50 nm, such as at least 75 nm, suchas at least 100 nm, such as at least 110 nm, such as at least 120 nm,such as at least 150 nm, such as at least 200 nm.

In another non-limiting embodiment, the protective coating 70 cancomprise a multi-layer structure, e.g., a first layer with at least onesecond layer formed over the first layer. In one specific non-limitingembodiment, the first layer can comprise alumina or a mixture or alloycomprising alumina and silica. For example, the first layer can comprisea silica and alumina mixture having greater than 5 wt. % alumina, suchas greater than 10 wt. % alumina, such as greater than 15 wt. % alumina,such as greater than 30 wt. % alumina, such as greater than 40 wt. %alumina, such as 50 wt. % to 70 wt. % alumina, such as in the range of70 wt. % to 100 wt. % alumina and 30 wt. % to 0 wt. % silica, such asgreater than 90 wt. % alumina, such as greater than 95 wt. % alumina. Inone non-limiting embodiment, the first layer comprises all orsubstantially all alumina. The first layer can have a thickness in therange of greater than 0 nm to 1 micron, such as 5 nm to 10 nm, such as10 nm to 25 nm, such as 10 nm to 15 nm. The second layer can comprisesilica or a mixture or alloy comprising silica and alumina. For example,the second layer can comprise a silica and alumina mixture havinggreater than 40 wt. % silica, such as greater than 50 wt. % silica, suchas greater than 60 wt. % silica, such as greater than 70 wt. % silica,such as greater than 80 wt. % silica, such as in the range of 80 wt. %to 90 wt. % silica and 10 wt. % to 20 wt. % alumina, e.g., 85 wt. %silica and 15 wt. % alumina. The second layer can have a thickness inthe range of greater than 0 nm to 2 microns, such as 5 nm to 500 nm,such as 5 nm to 200 nm, such as 10 nm to 100 nm, such as 30 nm to 50 nm,such as 35 nm to 40 nm. In another non-limiting embodiment, the secondlayer can have a thickness in the range of greater than 0 nm to 1micron, such as 5 nm to 10 nm, such as 10 nm to 25 nm, such as 10 nm to15 nm. In another non-limiting embodiment, the protective coating 70 canbe a bilayer formed by one metal oxide-containing layer (e.g., a silicaand/or alumina-containing first layer) formed over another metaloxide-containing layer (e.g., a silica and/or alumina-containing secondlayer). The individual layers of the multi-layer protective coating canbe of any desired thickness. Non-limiting examples of suitableprotective coatings 70 are described, for example, in U.S. patentapplication Ser. Nos. 10/007,382; 10/133,805; 10/397,001; 10/422,094;10/422,095; and 10/422,096.

The protective coating 70 can be positioned over the overcoat 60.Alternatively, the protective coating 70 can be positioned under theovercoat 60, for example between the overcoat 60 and the seconddielectric layer 50. Or, the overcoat 60 can be eliminated and theprotective coating 70 used instead of the overcoat 60, i.e., theprotective coating 70 is provided over the second dielectric layer 50.

An optional second primer layer (not shown) can be positioned betweenthe first dielectric layer 40 and the metallic layer 46. The optionalsecond primer layer can be formed of any of the materials describedabove for the first primer layer 48. For example, the optional secondprimer layer can be titanium having a thickness in the range of 0.5 nmto 2 nm, such as 1 nm to 2 nm, such as 1.5 nm.

Another non-limiting coating 100 of the invention is shown in FIG. 3.This exemplary coating 100 includes a base layer or first dielectriclayer 102 deposited over at least a portion of a major surface of asubstrate (e.g., the No. 3 surface 20 of the second ply 18). The firstdielectric layer 102 can be a single layer or can comprise more than onefilm of antireflective materials and/or dielectric materials, such as,but not limited to, metal oxides, oxides of metal alloys, nitrides,oxynitrides, or mixtures thereof. The first dielectric layer 102 can betransparent to visible light. Examples of suitable metal oxides for thefirst dielectric layer 102 include oxides of titanium, hafnium,zirconium, niobium, zinc, bismuth, lead, indium, tin, and mixturesthereof. These metal oxides can have small amounts of other materials,such as manganese in bismuth oxide, tin in indium oxide, etc.Additionally, oxides of metal alloys or metal mixtures can be used, suchas oxides containing zinc and tin (e.g., zinc stannate), oxides ofindium-tin alloys, silicon nitrides, silicon aluminum nitrides, oraluminum nitrides. Further, doped metal oxides, such as antimony orindium doped tin oxides or nickel or boron doped silicon oxides, can beused. The first dielectric layer 102 can be a substantially single phasefilm, such as a metal alloy oxide film, e.g., zinc stannate, or can be amixture of phases composed of zinc and tin oxides or can be composed ofa plurality of films.

The first dielectric layer 102 (whether a single film or multiple filmlayer) can have a thickness in the range of 20 nanometers (nm) to 70 nm,such as 20 nm to 60 nm, such as 30 nm to 60 nm, such as 40 nm to 55 nm,such as 44 nm to 48 nm, such as 47 nm.

The first dielectric layer 102 can comprise a multi-film structurehaving a first film 104, e.g., a metal alloy oxide film, a second film106, e.g., a metal oxide or oxide mixture film, deposited over the firstmetal alloy oxide film 104, a third film 108, e.g., a metal alloy oxidefilm, and a fourth film 110, e.g., a metal oxide or oxide mixture film,deposited over the third metal alloy oxide film 104. The first film 104and the third film 108 can comprise zinc stannate. The second film 106and fourth film 110 can comprise zinc oxide, for example, 90 wt. % zincoxide and 10 wt. % tin oxide.

For example, the first film 104 and the third film 108 can be zincstannate, with each film having a thickness in the range of 5 nm to 25nm, such as 10 nm to 20 nm, such as 15 nm to 20 nm, such as 15 nm to 17nm, such as 16 nm to 17 nm. The films do not have to be of the samethickness. The second film 106 and the fourth film 110 can be zinc oxide(for example, 90 wt. % zinc oxide and 10 wt. % tin oxide) and each filmcan have a thickness in the range of 3 nm to 10 nm, such as 4 nm to 8nm, such as 5 nm to 8 nm, such as 6 nm to 8 nm. The films do not have tobe of the same thickness. For example, the second film can be thickerthan the fourth film.

A heat and/or radiation reflective metallic layer 112 is deposited overthe first dielectric layer 102 and can be as described above for themetallic layer 46. In one embodiment, the reflective layer 112 comprisesmetallic silver having a thickness in the range of 3 nm to 8 nm, such as4 nm to 8 nm, such as 5 nm to 7 nm, such as 6 nm to 7 nm. The metalliclayer 112 is a continuous layer.

A primer layer 114 is located over the reflective layer 112. The primerlayer 114 can be as described above for the primer layer 48. Forexample, the primer layer 114 can be titanium and can have a thicknessin the range of 0.5 to 5 nm, such as 1 nm to 5 nm, such as 2 nm to 5 nm,such as 3 nm to 4 nm.

A second dielectric layer 120 is located over the reflective layer 112(e.g., over the first primer layer 114). The second dielectric layer 120comprises one or more metal oxide or metal alloy oxide-containing films,such as those described above with respect to the first dielectric layer40. For example, the second dielectric layer 120 can include a firstmetal oxide film 122, e.g., a zinc oxide film, a second metal alloyoxide film 124, e.g., a zinc stannate film, a third metal oxide film126, e.g., a zinc oxide film, and a fourth metal alloy oxide film 126,e.g., a zinc stannate film.

The second dielectric layer 120 can have a total thickness (e.g., thecombined thicknesses of the layers) in the range of 10 nm to 50 nm, suchas 20 nm to 50 nm, such as 30 nm to 50 nm, such as 30 nm to 40 nm, suchas 30 nm to 35 nm.

For example, each of the zinc oxide films 122 and 126 can have athickness in the range of 3 nm to 15 nm, such as 3 nm to 10 nm, such as3 nm to 5 nm, such as 4 nm to 5 nm. The films do not have to be of thesame thickness. The metal alloy oxide (zinc stannate) layers 124 and 128can have a thickness in the range of 5 nm to 20 nm, such as 5 nm to 15nm, such as 10 nm to 15 nm, such as 11 nm to 12 nm. The films do nothave to be of the same thickness.

An overcoat 140 can be located over the second dielectric layer 120. Theovercoat 140 can be as described above for the overcoat 60. For example,the overcoat 140 can be titania having a thickness in the range of 1 nmto 10 nm, such as 2 nm to 8 nm, such as 4 nm to 8 nm, such as 6 nm to 8nm.

An optional protective coating 150 can be provided. The protectivecoating 150 can be as described above for the protective coating 70. Theprotective coating 150 can be positioned over the overcoat 140, underthe overcoat 140, or can be used instead of the overcoat 140.

The coating 30, 100 when used to make a reference insulating glass unit(“IGU”) having two panes of 3 mm clear glass, a 0.5 inch gap between thetwo panes filled with argon gas, and the coating 30, 100 on the No. 3surface of the IGU (i.e. on the outer surface of the inner glass pane)can achieve a performance of SHGC greater than or equal to 0.60, such asgreater than or equal to 0.62, such as greater than or equal to 0.63,such as greater than or equal to 0.65, such as greater than or equal to0.66, such as greater than or equal to 0.67, such as greater than orequal to 0.70, such as greater than or equal to 0.75, and a U-value lessthan or equal to 0.40, such as less than or equal to 0.38, such as lessthan or equal to 0.36, such as less than or equal to 0.35, such as lessthan or equal to 0.34, such as less than or equal to 0.33, such as lessthan or equal to 0.32, such as less than or equal to 0.30, such as lessthan or equal to 0.28.

The neutral high transmission coating of the present invention is alsowell suited as a coating for use in a triple glazed IGU 80, as shown inFIG. 3. The IGU 80 of FIG. 3 is similar to that of the IGU 10 of FIG. 1but includes a third ply 82 spaced from the second ply 18. The third ply82 has an outer surface 84 (No. 5 surface) and an opposed second majorsurface 86 (No. 6 surface). The coating 30 or 100 of the invention canbe deposited over the No. 5 surface. Another coating 88 can also beincorporated into the IGU 80. In one non-limiting embodiment, thecoating 88 can be the same as the coating 30 or 100. For example, thecoating 30 or 100 can be formed over at least a portion of the No. 5surface and the coating 88 (the coating 30 or 100) can be formed over atleast a portion of the No. 2 or No. 3 surface to provide a high SHGC. Inanother non-limiting embodiment of the invention, to achieve a lowerSHGC IGU with high visible light transmission and low U-value, thecoating 30 or 100 can be as described above but the coating 88 can be alower SHGC coating. For example, the coating 88 can include two or moremetallic silver layers, such as three or more metallic silver layers,such as four or more metallic silver layers. Examples of suitable lowerSHGC coatings include SOLARBAN® 60 coating (including 2 silverreflecting layers) or SOLARBAN® 70XL coating (including 3 silverreflecting layers), both commercially available from PPG Industries Inc.of Pittsburgh, Pa. For example, the coating 30 or 100 of the inventioncan be positioned on the No. 4 or No. 5 surface of the IGU 80 and thelower SHGC coating 88 can be positioned on the No. 2 surface. Thecoating 88 can have a lower emissivity than the coating 30 or 100. Forexample, the coating 30 or 100 of the invention has an emissivity ofless than or equal to 0.15, such as less than or equal to 0.1. Thesecond coating 88 can have an emissivity of less than or equal to 0.1,such as less than or equal to 0.05.

The following Examples illustrate various embodiments of the invention.However, it is to be understood that the invention is not limited tothese specific embodiments.

EXAMPLES

Table 1 illustrates embodiments of a coating stack of the presentinvention. In each example, the reflective layer is silver, the primerlayer is titanium oxide, the protective layer is titanium oxide, and thedielectric layers include sublayers of Zn₂SnO₄ and Zn0 (90 wt. % zincoxide and 10 wt. % tin oxide), wherein the Zn0 sublayer is positionedtoward the silver layer. The Zn0 sublayer is in the range of 5 to 15 nm.The performance data for each coating is based on an argon gas filledIGU configured as described above. The color coordinates a*, b*, and L*are those of the conventional CIE (1931) and CIELAB systems that will beunderstood by one of ordinary skill in the art. The color of thecoatings is neutral to blue in reflection. The SHGC and U-values are forthe reference IGU described above.

The coating stacks in Examples 1 and 3 are for an annealed glassproduct, i.e., the coated glass is not heated to the temperingtemperature of the glass substrate 10 (approximately 1200° F.). If thecoating is heated to the tempering temperature of the glass substrate,the coating stack will break down and exhibit a haze. The coating stacksin Examples 2 and 4 are for a tempered glass product, i.e., the coatingreaches the desired performance characteristics after tempering of thecoated glass substrate.

TABLE 1 Layer Thickness (nm) Coating Stack Ex. 1 Ex. 2 Ex. 3 Ex. 4 Range1^(st) Dielectric Layer 44.9 47.6 45.1 47 40-55 Reflective Layer 6.8 76.9 6.9 5.5-8.5 Primer 1.4 4.5 1.4 4.5 0.5-6  2^(nd) Dielectric Layer 3529.3 36.2 30.9 15-45 Protective Layer 5 6.9 5 6.9  0-15 Performance SHGC0.68 0.68 U-value 0.27 0.27 Color on monolithic clear glass T Rf Rg Ex.1 L* 94.7 30.5 32.5 a* −1.0 −1.2 −1.8 b* 1.1 −1.9 −5.1 Ex. 2 L* 94.430.4 32.8 a* −0.6 −0.4 −1.2 b* 1.2 −2.2 −6.9 Ex. 3 L* 94.6 30.4 32.7 a*−1.1 −0.5 −1.5 b* 1.3 −3.9 −6.4 “T” means transmitted color “Rf” meansreflected color from the film side “Rg” means reflected color from theglass side

A coating stack of the type shown in annealed Examples 1 and 3 can bematched with respect to its color and performance with a temperablecoating with similar layers, e.g., of the type shown in Examples 2 and4. However, to achieve the match, (a) the thickness of the primer layer48 of the annealed coating is increased (e.g., comparing Example 1 toExample 2, the primer layer 48 thickness is roughly doubled) to allowthe primer layer to getter oxygen during heating, (b) the thickness ofthe protective layer 60 of the annealed coating is increased to provideadditional durability, and (c) the thickness of the second dielectriclayer 50 of the annealed coating is reduced to compensate optically forthe increased thickness of the primer layer 48 and the protective layer60.

Example 5

A coating was modeled having the following structure:

TABLE 2 material thickness (nm) zinc stannate 16.6 zinc oxide 7.6 zincstannate 16.6 zinc oxide 6.8 metallic silver 6.4 titanium 3.4 zinc oxide4.7 zinc stannate 11.4 zinc oxide 4.3 zinc stannate 11.7 Titania(overcoat) 7.3

The coating had the following color coordinates:

TABLE 3 T Rf Rg L* 95.2 29.7 31.4 a* −0.7 −0.7 −1.4 b* 1.3 −3.4 −6.6

This coating provided reference IGU values of 0.27 SHGC and 0.68U-value.

It should be appreciated that the SHGC can be increased further by usinglow-iron glass, e.g., STARPHIRE® glass, Solarphire® glass, andSolarphire PV® glass, all commercially available from PPG Industries,Inc., Pittsburgh, Pa., as one or more of the glass panes in the IGU,such as the outer pane. In addition, the U-value can be affected by thechoice of gas in the air gap, e.g., switching the gas from argon to airwill increase the U-value.

It will be readily appreciated by those skilled in the art thatmodifications may be made to the invention without departing from theconcepts disclosed in the foregoing description. Accordingly, theparticular embodiments described in detail herein are illustrative onlyand are not limiting to the scope of the invention, which is to be giventhe full breadth of the appended claims and any and all equivalentsthereof.

The invention claimed is:
 1. A coated transparency, comprising: a. afirst substrate having a No. 1 surface and a No. 2 surface; b. a secondsubstrate spaced from the first substrate, with a gas-filled gap betweenthe first substrate and the second substrate, the second substratehaving a No. 3 surface and a No. 4 surface, with the No. 3 surfacefacing the No. 2 surface; and c. a coating formed over at least aportion of the No. 3 surface and defining a side of the gas-filled gapopposite the No. 2 surface, the coating comprising; i. a firstdielectric layer formed over at least a portion of the No. 3 surface,wherein the first dielectric consists of a first film, and a second filmin direct contact over at least a portion of the first film; ii. acontinuous metallic layer formed over at least a portion of the firstdielectric layer, the metallic layer having a thickness less than 8 nm;iii. a primer layer formed over at least a portion of the metalliclayer; iv. a second dielectric layer formed over at least a portion ofthe primer layer; and v. an overcoat formed over at least a portion ofthe second dielectric layer, wherein the coated transparency has a solarheat gain coefficient greater than or equal to 0.6 and a heat transfercoefficient less than or equal to 0.35, and wherein the gas-gap isfilled with air or a non-reactive gas.
 2. The transparency of claim 1,wherein the first film comprises zinc oxide and wherein the second filmcomprises zinc stannate; and wherein the first dielectric layer has athickness in the range of 40 nm to 50 nm.
 3. The transparency of claim2, wherein the second film has a thickness in the range of 3 nm to 15nm.
 4. The transparency of claim 1, wherein the metallic layer comprisessilver having a thickness less than or equal to 7.5 nm.
 5. Thetransparency of claim 1, wherein the second film comprises TiO_(x) andthe first film zinc stannate, and wherein the second dielectric layerhas a thickness in the range of 30 nm to 40 nm.
 6. The transparency ofclaim 5, wherein the second film has a thickness in the range of 3 nm to15 nm.
 7. The transparency of claim 1, wherein the overcoat comprisestitania and has a thickness in the range of 2 nm to 6 nm.
 8. Thetransparency of claim 1, wherein the first film comprises zinc stannateand the second film comprises TiO_(x).
 9. The transparency of claim 8,wherein the first dielectric layer has a thickness in the range of 44 nmto 48 nm, the first film has a thickness in the range of 16 nm to 17 nm,and the second film has a thickness in the range of 6 nm to 8 nm. 10.The transparency of claim 1, wherein the second dielectric layercomprises a first film comprising TiO_(x) and a second film comprisingzinc stannate.
 11. The transparency of claim 10, wherein the seconddielectric layer has a thickness in the range of 30 nm to 35 nm, thefirst film has a thickness in the range of 3 nm to 5 nm, and the secondfilm has a thickness in the range of 11 nm to 12 nm.
 12. Thetransparency of claim 1, wherein the second substrate is a glasssubstrate, wherein the first dielectric layer has a thickness in therange of 40 nm to 50 nm, the second film has a thickness in the range of3 nm to 15 nm, and the first film has a thickness in the range of 25 nmto 40 nm, wherein the metallic layer comprises silver having a thicknessless than or equal to 7.5 nm, wherein the primer film comprisestitanium, wherein the second dielectric layer comprises a TiO_(x) filmand a zinc stannate film deposited over the zinc oxide film, the seconddielectric layer has a thickness in the range of 30 nm to 40 nm, and thezinc oxide film has a thickness in the range of 3 nm to 15 nm, whereinthe overcoat has a thickness in the range of 2 nm to 6 nm and theovercoat comprises titania, and wherein the solar heat gain coefficientis greater than or equal to 0.65 and the heat transfer coefficient isless than or equal to 0.33.
 13. The coated transparency of claim 1,wherein the second substrate is a glass substrate, wherein the firstfilm comprises zinc stannate, and the second film comprises TiO_(x),wherein the first dielectric layer has a thickness in the range of 44 nmto 48 nm, the first film has a thickness in the range of 16 nm to 17 nm,and the second film has a thickness in the range of 6 nm to 8 nm,wherein the metallic layer comprises silver having a thickness less thanor equal to 7 nm, wherein the primer film comprises titanium, whereinthe second dielectric layer comprises a first film comprising TiO_(x), asecond film comprising zinc stannate, wherein the second dielectriclayer has a thickness in the range of 30 nm to 35 nm, the first film hasa thickness in the range of 3 nm to 5 nm, and the second film has athickness in the range of 11 nm to 12 nm, wherein the overcoat has athickness in the range of 5 nm to 10 nm and the overcoat comprisestitania, and wherein the solar heat gain coefficient is greater than orequal to 0.65 and the heat transfer coefficient is less than or equal to0.35.
 14. A coated transparency, comprising: a. a first substrate havinga No. 1 surface and a No. 2 surface; b. a second substrate spaced fromthe first substrate, with a gas-filled gap between the first substrateand the second substrate, the second substrate having a No. 3 surfaceand a No. 4 surface, with the No. 3 surface facing the No. 2 surface;and c. a coating formed over at least a portion of the No. 3 surface anddefining a side of the gas-filled gap opposite the No. 2 surface, thecoating comprising; i. a first dielectric layer formed over at least aportion of the No. 3 surface; ii. a continuous metallic layer formedover at least a portion of the first dielectric layer, the metalliclayer having a thickness less than 8 nm; iii. a primer layer formed overat least a portion of the metallic layer; iv. a second dielectric layerformed over at least a portion of the primer layer, wherein the seconddielectric consists of a first film, a second film over at least aportion of the first film, a third film over at least a portion of thesecond film, and a fourth film over at least a portion of the thirdfilm, wherein the first film of the second dielectric layer has athickness in the range of 3 nm to 5 nm; and v. an overcoat formed overat least a portion of the second dielectric layer, wherein the coatedtransparency has a solar heat gain coefficient greater than or equal to0.6 and a heat transfer coefficient less than or equal to 0.35.
 15. Thecoated transparency according to claim 14, wherein the first dielectriclayer has a thickness in the range of 40 nm to 50 nm.
 16. The coatedtransparency according to claim 14, wherein the second dielectric layerhas a thickness in the range of 15 nm to 45 nm.
 17. The coatedtransparency according to claim 14, wherein the first film comprisesTiO_(x), and the second film comprises zinc stannate.
 18. The coatedtransparency according to claim 14, wherein the first dielectric layercomprises a first film and a second film over at least a portion of thefirst film.
 19. The coated transparency according to claim 14, whereinthe second film in the second dielectric layer comprises TiO_(x), andwherein the fourth film in the second dielectric layer comprisesTiO_(x).
 20. The coated transparency according to claim 14, wherein thesolar heat gain coefficient greater than or equal to 0.65 and the heattransfer coefficient less than or equal to 0.33.